Process of making heat-exchange elements



g- 1941- H. E. SCHANK r-rrm. ,252,209

PROCESS OF MAKING HEAT-EXCIANGE ELEMENTS Filed NOV. 16, 1939 3Sheets-Sheet 1 Aug. 12,- 1941. H, E, SCHANK HAL 2,252,209

PROCESS OF MAKING HEAT-EXCHANGE ELEMENTS v Filed Nov. 16, 1939 3Sheets-Sheet-Z 1/ fiwxzwiors; fla /"y Z 5m Paul R. Seam? Aug. 12, 1941.H. E. SCHANK ETAL 2,252,209

PROCESS OF MAKING HEAT-EXCHANGE ELEMENTS Filed Nov. 16, 1939 3Sheets-Sheet 5 )l!) I III LI L. l l

Patented Aug. 12, 1941 PROCESS OF MAKING HlgAT-EXCHANGE ELEMENT Harry E.Schank and Paul R. Seemiller, Detroit, Mich., assignors to McCordRadiator .8; Mtg. 00., Detroit, Mich a corporation of Maine ApplicationNovember 16, 1939, Serial No. 304,656

3 Claim.

This invention relates to a process of making a heat-exchange element.The heat-exchange element has been developed for use in radiator coresbut it may be used in cooling apparatus as well. For convenience, itwill be reierred to as a fin element" because it performs heatdissipating functions such as performed by fins.

The object of the invention is to provide an improved process of makinga heat-exchange element.

Other objects and advantages oi the invention will appear irom thefollowing specification and drawings.

An embodiment. oi the invention is illustrated in the accompanyingdrawings in which:

Figure 1 is a perspective of a roll of sheet metal such as used tomakethe fin element.

Fig. 2 is a perspective view of the metal sheet after it has beensubjected to the first forming operation.

Fig. 3 is a partial cross-section of a portion of the heat-exchange finsection showing how its folds can be pressed together in the process ofmaking it.

Fig. 4 is a section similar to Fig. 3 showing the folds in the completedcondition of the fin section.

Fig. 5 is a perspective view of the completed heat-exchange fin element.

Fig. 6 is a partial view of a radiator core showing how the fin elementis employed.'

Fig. 7 is a top plan view of two sets of folds of the fin elementillustrating more clearly how the projections are formed therein.

Fig. 8 is a side elevation of one of the folds of the fin section, theview being taken along the line l8 of Fig. 7.

Fig. 9 is a section along the line 99 of Fig. '7.

Fig. 10 isa section along the line iii-i0 of in-part of our priorapplication Serial No. 280,-

133, filed June 20, 1939.

Heat-exchange fins are used by placing them in'contact with the walls ofa passage through which a heated medium is being passed in order thatheat may be conducted from the walls to the fins and thus provide moresurface over make elements of this kind. And the metal haswhich air maybe passed to dissipate the heat. This general type of construction hascome into very extensive use in automotive, refrigerating,

heating, ventilating, andallied industries with the result thatheat-exchange fins must be rapidly produced ln enormous quantities. Theproblem involved is to produce a fin element that can be convenientlyand easily assembled in the article with which it is to be used; onethat is efficient in its heat-exchange action; one that is made of aminimum amount of metal; and one that can be made by an inexpensiveprocess on a quantity production basis.

Heat-exchange fin elements have heretofore been made out of relativelystlfl, hard metal of appreciable thickness. The metal employed is whatis known as "silver-bearing copper, the

supply of which is limited and the cost higher than that of ordinarycopper. The silver in the copper gives it the required stiffness. Themetal has had to be relatively thick in order that it might be stampedor drawn into shape which is the process that generally has beenemployed to had to be hard and stiff in order that the finished articlewill hold its shape. The result has ess used in making the heat-exchangeelements and the nature of the elements themselves.

The present invention involves a fin element that is made out of verythin, soft metal but which, nevertheless, is made in such a way that thefinished element has ample strength for assembly in the article forwhich it is used and at the same time has the required heatexchangecharacteristics. It is not necessary to use a silver-bearing copper.Instead, ordinary and less expensive copper may be employed. And, aswill presently appear, the element may be made by an improved processthat is both rapid and simple. The result is that a fin element isproduced in which the amount of material used is substantially less thanthat herebefore employed, thereby reducing costs, and the element may beproduced by a process that. en-

The element is made out of a thin strip of sheet metal l0, shown in Fig.1, which is preferably in the form of a continuous strip or roll iii asillustrated. Preferably this strip has a width in the direction A(Fig. 1) equal to the thickness of the core with which the heat exchangeelement is to be assembled. For example, if the element is to be used ina radiator core on an automobile, the width of the metal strip is equalto the thickness of the core.

The metal usually employed is ordinary soft copper although brass andsimilar metals may also be used. Instead, however, of using relativelyhard and stiff copper, a soft pliable copper having a thickness of aboutthree thousandths (.003) of an inch is used as compared with the formerpractice of using hard, stiiI copper ofat least four thousandths (.004)of an inch thick which thickness has heretofore been considered theminimum possible to employ in commercial practice. While the differencein actual fractions of an inch is not great, this difference is a verydecided one in its effect on the amount of metal consumed when quantityproduction of these elements is considered.

The first operation is to form the strip into the shape shown in Fig. 2.This forming operation is a continuous one and it is a rolling operationas distinguished from stamping, the strip of soft copper being fedcontinuously between rollers, as later will be explained.

In this first step, the strip is reversely folded or rolled to a shapein which the folds H are substantially at right angles to one anotherand not in the final condition desired. This angle should be as close to90 as possible but can be as low as 80. It is to be observed that thebends l2 are not along sharp lines but are gradual, rounded bends whichenable the metal to be rolled to shape without requiring that it bedrawn, and avoiding splitting and cracking as might occur with theextremely thin metal employed. The bends also have a substantial widthto provide ample areas of contact with the tubes to which the finelements are attached.

At the time the strip is roll-folded to the shape of Fig. 2, a pluralityof indentations or bumps I8 of substantial depth are also formed in it.These are about three thirty-seconds of an inch (is) deep and in theshape of truncated pyramids and they alternate across the width of thestrip both as to the direction in which they are formed and as to theirheight relative to the edges of the folds. For example, referring toFig. 5, the first bump or indentation IS on the right-hand end of thefirst fold is toward the upper edge of the fold and it extends towardthe person viewing the figure, while the next bump to the left ispositioned toward the bottom of the fold and extends away from theperson viewing the figure. The bumps or indentations thus alternate indirection and location across the width of the fold. The purpose ofthese bumps or indentations will be explained at the time the completedheat-- exchange element is described.

Also, at the time the metal strip is roll-folded to the shape of Fig. 2,a plurality of spacing bumps ll may be formed for use in a subsequentstep in one form of the process of making the element. These bumps orindentations also alternate as to their direction with respect to thefaces ofthe folds and as to their height relative to the edges .of thefolds, as will be clear from Figs. 2 and 5. The bumps are located sothat those on one fold are in position to contact those on the foldimmediately adjacent, as indicated in Figs. 3 and 4. From these figuresit might be inferred that the spacing bumps would act as to every otherbend only but the fact is that, if another sectional view were takenthrough the next set of spacing bumps, the bumps that space the middlebends of Figs. 3 and 4 would appear. In other words, there are spacingbumps between each fold to control each bend of the element. While-thesespacing bumps may be formed as illustrated and just described, it isalso possible to form them so that, instead of having one spacing bumpon one fold contact a spacing bump on another fold, the spacing bump onone fold is made deep enough so that it may contact the surface of theadjacent fold without said surface being provided with a bump forcontacting the first bump.

The next step in the process consists in compressing the reverselyfolded strip of Fig. 2 to move the folds toward one another with theultimate object of having the folds substantially parallel to oneanother as shown in the completed element illustrated in Fig. 5. Thedegree and nature of the compression determines the spacing of the foldsand it is in this connection that the spacing bumps it can be employed.During the second forming operation, the folds are compressed togetheruntil the spacing bumps it contact one another as shown in Fig. 3, thefinal form of the element being determined by the height of the bumps.It has been found, for example, that, with the folds made out of .003"soft copper, when the folds are compressed until the bumps it contactone another, as shown in Fig. 3, if the folds are then released theywill spring apart to a position such as shown in Figs. 4 and 5. Byvarying the height of the spacing bumps if, the degree to which thefolds are compressed together can be regulated and the width or spacebetween the folds after they have sprung apart can be governed. Thefrequency of the folds is usually about ten per lineal inch, but thismay be varied, preferably being kept, however, between nine and twelveper inch for the best results.

The above process provides an easy and convenient means of determiningthe final spacing of the folds, but this spacing can be otherwisedetermined by regulating the degree to which the folds are pressedtogether as presently will be explained, the spacing bumps beingespecially useful in forming narrow fin sections. The spacing bumps arealso useful in maintaining the folds spaced from one another during theassembly of the fin elements in a core, particularly in the cellulartype of radiator core.

In order that the process may be more completely and easily understood,it will be explained in connection with a form of apparatus that may beused for practicing it, said apparatus being illustrated in Figs. 11 to13, inclusive.

Referring to Fig. 12, the metal strip l0, out of which the heat-exchangeelement is formed, is passed between guides 20 to two intermeshing,toothed, forming rolls 2|. These rolls are made up of a series of disks2| (Fig. 11) and they have teeth 22 formed in them with suitable humps23 so that, as the strip i 0 passes between the rolls,

' it is rolled or formed to the reverse-folded shape illustratedin Fig.2. Not all the bumps are shown in Fig. 11 because of the confusion oflines that would result. The edges of the teeth are rounded and theteeth join one another by curved surfaces to make the bends in the metalrounded or curved and of substantial width. It is to be noted that thisoperation is primarily a rolling operation as distinguished from drawingor stamping though a slight drawing occurs during the rolling. Thisample up to two inches (2"), though the depth rarely exceedsthree-fourths of an inch for ordinary purposes. A depth ofseven-sixteenths of an inch (1%") is average for automobile radiatorscores. These depths have not heretofore been considered possible in arolling operation with metal as soft and thin as that employed in thepresent invention.

As the partially formed strip l issues from the rolls II and 22, itpasses into a guide having a bottom plate 30 (Fig. 12) and a top plate3| supported by side rails 32 (Fig. 11). The top plate 3| is slidablymounted in grooves'in the side rails 32 and releasably held in positionnear its front end by washers-33 that maybe clamped against the topplate by bolts 34 screw-threaded into the side rails. The top plate isheld in position toward the rear by a crossbar 34 bolted to the side athe block 33. The top plate 3| is provided with sight openings 33 atfront and rear to enable the operator to observe the partially formedstrip as it issues -from the forming and gathering rolls.

A gathering roll 40 is journaled in position under the guide 30-3l asshown in Fig. 12, the axis of said roll being substantially in the sameplane as the axis of the lower forming roll 2|. The gathering roll 40 isof the same size and general construction as the forming rolls and 2|except that the alternate disks (Fig. 12) which, in the forming. rolls,have humps 23 on them, are made of small diameter so as not to engagethe fin element. They act as spacing disks leaving the other disks toadvance the fin element. This reduces the cost of the gathering rolland, at the same time, provides a construction that will advance the finelement without deforming the humps already formed in it. The gatheringroll is driven at the same speed as the forming rolls and positioned sothat its teeth project through an opening in the bottom guide plate(Fig. 12) where they enter the spaces between the folds of the partiallyformed strip Was it passes through the guide. The gathering roll picksup the parat considerably slower speed. It is a toothed roll but thenumber :of teeth 3| is considerably greater 7 "the number in'thegathering roll and the jt'e 'elth are smaller, asshown in Fig. 12. Thegears ffor drivingthe several rolls have not been illustrated. as thesemerely comprise the necessary spur gears to drive the forming rolls andthe gathering roll at the same speed, with the spacing roll driven insynchronism, but at a slower speed, and with provisions for varying thespeed of the spacing roll relative to the other rolls. In fact, thediameter of the spacing roll 30, its

speed, and the number of teeth in its circumference are factors that canbe varied to suit the spacing requirements of the fin element beingformed,

Positioned above the spacing roll 30 is a curved guide 32 that conformsgenerally to the curve of the spacing roll. This guide is supported bythe side rails 32 which are elevated for the purpose at the rear of themachine. The guide 32 is resiliently held in position by springs 33bearing against the guide and against nuts 54 on bolts 33 that arethreaded into the side rails. A plate 38 extends to the rear of themachine to receive the finished fin element strip. The curved guide. 32

has sight openings 31 (Fig. 11) to permit the operator to observe thefin element on the spacing roll and in finished condition.

, Keeping in mind that the spacing roll 30 moves at a slower speed thanthe gathering roll 40 it will be clear that. as the reverse-folded stripmoves rearward, the spacing roll will retard it while the gathering rollwill keep feeding it rearward at a greater speed. The fin element isgathered at the same speed at which it is delivered by the spacing roll,the difference in speed of the tworolls causing the gathering. Theresult is that the folds of the fin strip are continuously moved orcompressed toward one another and the degree of this compressiondepends, of course, upon the relative speed of the gathering and spacingrolls. When the spacing bumps are formed on the fin strip, the folds arepressed together until the spacing bumps contact. When no spacing bumpsare used, the folds are compressed together until they contact'eachother as shown in Fig. 12. In all cases, the metal has sumcientresiliency which, combined with the factthat the bends between folds arerounded and not sharp, enables the folds to spring apart sufficientl totheir proper parallel position.

When the strip, after being gathered as above I explained, is released,the folds will spring apart with a reasonable degree of accuracy that issufficient in some cases, but provision is made for insuring that thefolds will be accuratelylspace'd to the desired number of folds perinch.

' Referring to Fig. 12, the top 3| of the guide through which the finstrip passes is provided with a finger 80, preferably made of springsteel,

which projects beyond the rear end of the guide top 3|. This finger isof substantial width and its free end BI is curved as shown in Fig. 12,said curved end extending downward slightly beyond the top plate 3| ofthe guide. The spring finger is held in position on the top plate 3| bya lever 82 pivoted at 62* to a bearing block on the plate 3|. Theleft-hand end of said lever (Fig. 12) is urged upward by a spring 83 andthe other end of the lever is turned down so as to engage the springfinger Oil. The effective tension of the spring 33 may be regulated by athumb screw 64 which is threaded into a block on plate 3! and providedwith a collar bearing against lever 32. The spring finger 63 is held inposition on the plate 3| by a thumb nut BI.

For use in starting operations, two fingers l3 (Fig. 13) are providedwhich are carried by a head 'H slidably mounted on bolts 12 threadedinto the side rails 32 and urged upward by springs 13. In normalposition, the pins 10 are in the position of Fig. 13 where they are outof the path of the fin element. When the apparatus is started, theoperator presses down on the head 'II to move the pins I into the pathof the fin element where he holds them. until the folds have beencompressed to the desired degree, which the operator observes throughthe sight openings 39 at the rear of the plate 3|. He soon learns aboutwhat this compression should be, after which he releases the pins andthe process of forming the fin element then goes forward as a continuousone. The starting operation above described, while a convenient anduseful one in connection with the apparatus, is to be considered more ofa starting operation than a part of the continuous process.

Assuming that operations have been started, as the fin element issues atthe rear of the guide, the spring finger 60 engages one of the upperfolds and retards the element, this retarding action being a measurableone because the curved end of the spring 60 narrows the exit from theguide and tends to hold the fold against the bottom plate 30 of theguide. The spacing roll 50 picks up the lower bend of one of the foldsand moves it to the position shown in Fig. 12, the lower bend seating inone of the spaces between the teeth of the spacing roll. Theillustration of the fin element at the right-hand end of Fig. 12 isnecessarily diagrammatic because of the small space available for linesof the drawing. As this occurs, the resistance to the rearward movementof the fin element is governed by the spacing roll and the spring finger60, said spacing roll moving considerably slower than the gathering roll40. But, as the spacing roll continues to rotate and as increasedpressure is exerted by the gathering roll, the fold of the fin elementmoves past the spring finger into the guide 51. It will be noted thatresistance to th rearward movement of the fin element is exerted both atthe top and at the bottom of the element, the resistance at the topbeing by the spring finger 60 and that at the bottom by the spacing roll50. The amount of this resistance can be regulated to a considerabledegree by varying the position of and the tension on the spring finger60. Where greater variations are desired, the speed and number of teethin the spacing roll 50 can be changed.

Where spacing bumps, such as the bumps I4 are provided, the folds cannever be compressed beyond a certain amount determined by said spacingbumps although the degree of compression may be less than necessary totightly compress the bumps together.

When no spacing bumps are employed, the spacing of the folds isdetermined entirely by the degree of their compression, regulated asabove explained. Where the compression is relatively high, the radius ofthe bends between the folds is slightly less than where the compressionis smaller. This variation is very small in actual dimensions, owing tothe fact that there are usually at least ten folds per inch, making fivetop bends and five bottom bends over which the changes in radius aredistributed. Th spacing, as between nine and twelve folds per inch, canbe regulated by using different spacing rolls 50 for the differentspacings. Also, the spacing can be varied to the extent of at leastone-half a fold by means of the spring finger without changing thespacing roll 50.

The spacing is further regulated by the action charge guide 58. As thefin element, with its top bends yieidingly held against rearwardmovement by the finger Iii, issues from the guide iii-4|, it is bentupward by the spacing roll 50. This bending tends to separate the bottombends from one another and to open up the top bends to an extentdetermined by the adjustment of the finger 6|. The bottom bends are heldseparated by the spacing of the teeth on the spacing roll 50. As the finelement is bent downward again to a substantially horizontal position bythe curved guide 52 and the spacing roll, the top bends are separatedfrom one another and the bottom bends are opened. This occurs becausethe bottom bends are held in spaced relation by the teeth of the spacingroll, and the yielding of the fin element to the reverse bending opensup the bottom bends. This opening of the top and bottom bends can beregulated by the adjustment of the spring finger BI and by the spacingof the teeth on the spacing roll. It depends also upon the location anddiameter of the spacing roll which, of course, determines the curvatureof the bending in both directions.

Thus, while the resiliency of the metal tends to separate the foldsafter they have been pressed together, the above makes it possible toregulate this separation so as to get a fin element with its foldsaccurately spaced to the desired degree and with the folds substantiallyparallel to one another.

The apparatus shown is one apparatus by means of which the process maybe practiced. It has been found to be very simple and effective; but, asfar as the process is concerned, other types of apparatus may be used,the essential thing being that the fin strip be formed and continuouslygathered in such a manner that, when the folds are released, they willbe properly spaced apart the required distance with the foldssubstantially parallel with one another and in a vertical position,assuming the fin strip to be in a horizontal position.

The completed fin strip issues onto the guide 56 and passes through acutter (not shown) which may be employed to cut the strip into desiredlengths.

It will thus be seen that a continuous process has been developed forforming a fiat metal strip into a completed heat-exchange fin stripwithout requiring a large number of steps and without requiring anycomplicated or intricate steps. The width of the element may beregulated by the width of the metal strip that is employed and thespacing between the folds of the elements may be regulated by varyingthe degree to which the formed folds are pressed together. The foldingoperation is exceedingly simple and inexpensive, yet highly efiicientand rapid. The

.process enables soft copper to be used of considerably less thicknessthan that heretofore employed, with a marked reduction in the amount ofmetal used as well as enabling a less expensive metal to be employed.

A completed heat-exchange element isshown in Figs. 5 to 10, inclusive.It comprises a pleated element in which the folds are substantiallyparallel to one another, in which the edges of the folds are rounded andhave a substantial width for contact with the wallsof the passages from,

which the element is to conduct heat. and in location of these bumps orindentations is such that an undulating passage for the air is providedthat undulates not only in a vertical but also in a horizontal plane,or, to put it another way, a passage which undulates in two planes whichare at right angles to one another.

The manner in which the heat-exchange ele-. ment may be used is shown byway of example in Fig. 6 where the element is positioned between thetubes 80 of a tubular type of automobile radiator core. The substantialwidth of the edges of the folds enables ample contact to be made betweenthe fin elements and the sides of the tube, and the soft copperfacilitates-the making of intimate contact at the time the core isassembled. This createsan improved degree of air turbulence asdistinguished from an undulating passage in one plane only, and gives agreater area for air contact with the fin than where openings arepunched.

It is to be understood that the invention has been shown and describedby way of illustration only and that changes may be made therein withoutdeparting from the spirit and scope of the invention as defined by. theappended claims.

We claim:

1. The method of making in a. continuous stantially parallel relation,all of said operations being carried on simultaneously.

2. The method of making in a continuous process an accordion-pleated finelement having its folds substantially parallel with one another, whichconsists in moving endwise and reversely folding a metal strip with thebends between the folds rounded and of substantial width, progressivelypressing said folds together as they are formed until adjacent foldscontact with each other, progressively bending the compressed finelement in one direction a predtermined amount to effect a successiveopening up of the compressed folds on one side of the fin element, thenprogressively bending the partially opened portion of the fin element inthe opposite direction to open the bends on the other side of saidelement to thereby obtain a completed fin element with its foldsaccurately spaced in substantially parallel relation, all of saidoperations being carried fon simultaneously, and controlling the amountof separation of the folds by regulating the speed of movement of thestrip during said bending operations.

3. The method of making in a continuous process an accordion-pleated finelement having its folds substantially parallel with one another, whichconsists in moving endwise and reversely folding a metal strip with thebends between the folds rounded and of substantial width, progressivelypressing said folds together as they are formed until adjacent foldscontact with each other, progressively bending the compressed finprocess an accordion-pleated fin element having its folds substantiallyparallel with one another, which consists in moving endwise andreversely folding a metal strip with the bonds between the folds roundedand of substantial width, progressively pressing said folds together asthey are formed until adjacent folds contact with each other,progressively bending the compressed fin element in one direction apredetermined amount to effect a successive opening'up of the compressedfolds on one side of the fin element, and then progressively bending thepartially opened portion of the fin element in the opposite direction toopen the bends on the other side of said 1 element to thereby obtain acompleted fin element with its folds accurately spaced in subobtain acompleted fin element with its folds accurately spaced in substantiallyparallel relation,

all of said operations. being carried on simultaneously.

HARRY E. SCI-IANK.

PAUL R. SEEMILLER. g

